1. Technical Field
This invention relates to document printing and duplication. More particularly, this invention relates to a network for high-speed, parallel document printing and duplication.
2. Description of Related Art
Large offices and fast turn-around copy centers run multiple printers and copy machines in parallel to speed processing of printing and duplication. Conventionally, a digital input document is created on a scanner 103 or other input device. The digitized input document may then be sent through dedicated cables 101 to multiple laser printers 105 or other output devices as shown in FIG. 1(a).
Alternatively, as shown in FIG. 1(b), a network compatible scanner 104 or other input device may send the digitized input document to a local area network (LAN) 102, such as an Ethernet network, to network compatible laser printers 106 or other output devices. The scanner 104 shown in FIG. 1(b) may be, for example, a GP200 model digital copier available from Canon Inc.
Such networks 102 are conventionally operated by sending packets from the scanner 104 to each individual printer 106. An individual printer 106 receives from the network 102 those packets which have a destination address identifying the individual printer 106. Practically speaking, such a system is limited to about six (6) printers 106 when implemented via a 10 megabit per second Ethernet network 102.
Such a system is shown in FIG. 2. FIG. 2 is a schematic diagram showing the data 202 for a document xe2x80x9cnxe2x80x9d being sent over a conventional network 102 six (6) times by a scanner 104, in order to be received and printed by six (6) printers 106. In such a system, the data 202 transmitted over the network 102 must double in order to cause two printers 106 to each produce a copy of the same document. Data 202 transmitted must increase by a factor of N in order to cause N printers 106 to each produce a copy of the same document.
In particular, at a resolution of 600 dots per inch (dpi), an 8.5 inch by 11 inch monochrome scanned image (1 bit per scanned pixel) contains about 4.2 Mbytes of data. Transmitting 4.2 Mbytes of data across a typical 10 BaseT (10 megabits per second) Ethernet network takes approximately 5 seconds. This transmission time is too long and significantly impacts the speed at which multiple copies of the document are printed. The time may be reduced to about 0.5 second by compressing the data (e.g., via JBIG or Group 3 fax compression techniques). Nevertheless, transmitting twenty (20) compressed pages (each 4.2 Mbytes of data before compression) still requires about ten (10) seconds of network transfer time. This is still a substantially long time, which adversely affects system performance.
From the above discussion, it is apparent that what is needed is a system in which the network transfer time of a document to multiple printers is decreased in order to enhance the speed at which multiple copies may be printed.
In order to avoid the above discussed drawbacks, a high-speed, parallel document printing and duplication system sets up each of the multiple laser printers (106) with each a conventional individual network address and a new shared group network address. Each printer (106) xe2x80x9clistensxe2x80x9d to the network (102) for document data (402) sent to its group address. The assignment of printers (106) to sending devices (104) is controlled by a dynamic group addressing computer (302). Each printer (106) also may confirm receipt of document data (402) by sending a confirmation packet to the sending device (104). Such a system permits large numbers of printers (106) to receive each document without crowding the network (102) bandwidth and slowing system performance. Moreover, such a system enables dynamic reconfiguration of group assignments, which results in flexibility in the use of the multiple printers (106) to simultaneously print a number of jobs at various speeds.